In the packaging industry, tampering is the adulteration or change of the contents of a package. Unfortunately, the threat of tampering has become something that we as consumers accept as a necessary evil in making purchases today.

Since the initial incident of tampering with an over-the-counter medication for pain relief in the early 1980s, many other instances of tampering with medicines or foods have occurred. Today, it's essentially impossible to find a package of anything that has use for ingestion by humans that does not have a safety feature. Everything we buy that will go into our mouths is either tamper-evident or tamper-proof. What is the difference in these two approaches to ensuring product safety?

Tamper-evident means that a package that has undergone tampering will show some readily observable sign that the tampering has taken place; the sign may be audible or visible. A common example of an audible tamper-evident signal is actually the absence of any sound when opening a lid on a jar or bottle. Without hearing the characteristic “pop” when unscrewing the lid from a vacuum-sealed jar or bottle, a consumer should be suspicious and should not consume the package contents.

Another common example of a tamper-evident package is a bottle with a screw-on lid. Unscrewing and removing the lid reveals a covering over the bottle opening. This covering of film, paper, or some composite construction adheres to the rim of the bottle opening with a heat seal adhesive. Instructions on the package usually advise the purchaser to reject any package without an intact covering.

A shrinkable band or sleeve is another approach to tamper evidence. This involves wrapping a band or sleeve around a bottle or jar and its cap. The material is a heat-shrinkable film — one that fits tightly onto the bottle or jar when exposed to heat. The heat-shrinkable material generally contains instructions to reject the package if the sealing band or sleeve is not intact.

Other possible ways to approach tamper evidence in a package can involve something that undergoes a color change during any attempt at tampering or a specific alignment of markings on a package that cannot be duplicated.

Regardless of the technique used, the intent of making a package tamper-evident is to alert the consumer that something has happened to the package since its manufacture.

“Tamper-proof” is something completely different, although the difference in a package can be very subtle. When a manufacturer makes a tamper-evident package, the company is not saying that it's trying to avoid all attempts at physical tampering — it's saying that it simply wants to alert the consumer to any such attempts. “Tamper-proof,” however, is an effort by a manufacturer to prevent any success by someone who tries to tamper with the item.

Perhaps the best example of a tamper-proof package is a metal can. The only way someone could tamper with this package would be to open it. This would no longer be a consumer-acceptable package, and nobody would purchase an opened can from a store. This example shows the subtlety of a tamper-proof package. Nothing can ever be so tamper-proof that someone could not open it by some means. Complete inability to open a package invalidates the original intent of the package — protecting the contents of the package until opening, removal, and use.

Consider a small, flexible package holding two cookies. The intent of the package is to preserve the cookies and provide convenient handling before consumption. A tamper-proof package, i.e., one that could never be opened, would mean no one could tamper with the cookies, but no one could eat them either!

Thus, a better way to think of tamper-proof may be to consider it the highest degree of tamper-evident. Whatever you call it, resistance to and evidence of tampering are necessary components of packaging today.

David J. Bentley Jr. is a recognized industry expert in polymers, laminations, and coatings with more than 30 years of experience in R&D and technical service. Contact him at e-mail:This email address is being protected from spambots. You need JavaScript enabled to view it..